Pinus massoniana somatic embryo maturation, mycorrhization of regenerated plantlets and its resistance to Bursaphelenchus xylophilus

Abstract

Pine wilt disease, caused by the pine wood nematode (PWN, Bursaphelenchus xylophilus), is a major quarantine forest disease that poses a threat to various pine species, including Pinus massoniana (masson pine), worldwide. Breeding of PWN-resistant pine trees is an important approach to prevent the disease. To expedite the production of PWN-resistant P. massoniana accessions, we investigated the effects of maturation medium treatments on somatic embryo development, germination, survival, and rooting. Furthermore, we evaluated the mycorrhization and nematode resistance of regenerated plantlets. Abscisic acid was identified as the main factor affecting maturation, germination, and rooting of somatic embryos in P. massoniana, resulting in a maximum of 34.9 ± 9.4 somatic embryos per ml, 87.3 ± 9.1% germination rate, and 55.2 ± 29.3% rooting rate. Polyethylene glycol was identified as the main factor affecting the survival rate of somatic embryo plantlets, with a survival rate of up to 59.6 ± 6.8%, followed by abscisic acid. Ectomycorrhizal fungi inoculation with Pisolithus orientalis enhanced the shoot height of plantlets regenerated from embryogenic cell line (ECL) 20-1-7. Ectomycorrhizal fungi inoculation also improved the survival rate of plantlets during the acclimatization stage, with 85% of mycorrhized plantlets surviving four months after acclimatization in the greenhouse, compared with 37% non-mycorrhized plantlets. Following PWN inoculation, the wilting rate and the number of nematodes recovered from ECL 20-1-7 were lower than those recovered from ECL 20-1-4 and 20-1-16. The wilting ratios of mycorrhizal plantlets from all cell lines were significantly lower than those of non-mycorrhizal regenerated plantlets. This plantlet regeneration system and mycorrhization method could be used in the large-scale production of nematode-resistance plantlets and to study the interaction between nematode, pines, and mycorrhizal fungi.

Somatic embryogenesis of slash pine (Pinus elliottii Engelm.): initiation, maturation, germination and mycorrhization of regenerated plantlets

“…This study showed that various seed families exhibited significantly different capacities in initiating EC, with range 1.11-27.78%, and family 7# was more responsive than families 27# and 30#. Similar significant differences in EC initiation capacity among different pine families were also observed in P. elliottii (Liao and Amerson 1995a;Liao and Amerson 1995b;Yang et al 2020), P. taeda (Tang et al 2001;Pullman and Johnson 2002), P. pinaster (Miguel et al 2004;Park et al 2006), P. pinea (Carneros et al 2009, P. radiata (Hargreaves et al 2009), P. halepensis (Montalban et al 2013), hybrid P. elliottii × P. caribaea (Nunes et al 2018) and P. massoniana (Xia et al 2021;Chen et al 2023). The results described the influence of genotype on EC initiation rates, and future studies could explore a wider range of seed family at the initiation stage.…”

“…tinctorius and Boletus edulis (Wang et al 2015). And Zheng et al (2003), Zhu et al (2010) and Chen et al (2023) showed that using ectomycorrhizal fungi Pis. orientalis can promote plant development in P. massoniana.…”

“…As stated above, SE has been successful in many Pinus spp., but the currently available SE laboratory methods vary widely in their effectiveness across species and genotypes (Egertsdotter 2019). Numerous research efforts have been directed towards promoting the initiation or maturation through altering media formulations containing plant growth regulators, polyamines and hormone inhibitors (Pullman and Bucalo 2014;Peng et al 2021;Xia et al 2021;Chen et al 2023). The acclimatization stage is also viewed as a significant hurdle in the effective micropropagation of conifers.…”

Long-Term Successional Subculture Dynamics and Their Effects on the Proliferation Efficiency, Embryogenic Potential, and Genetic Stability of Embryogenic Tissues in Larix principis-rupprechtii Mayr

“…Consequently, these factors contribute to the inefficiency of Prince Rupprecht's larch breeding. The rapid progress in plant somatic embryogenesis has surmounted numerous challenges encountered in conventional sexual reproduction breeding methods, paving the path for the advancement of effective gene transfer technology and widespread propagation of new, high-performing clonal populations [7][8][9][10]. Research on somatic embryogenesis techniques in Pinus species commenced with the initial observation of embryo-like structures in Banks pine (Pinus banksiana) documented in 1976 [11].…”